Question:
Is it permitted for me to purchase this shampoo, which contains meat and milk ingredients? Does shampoo need to be kosher? I am aware that there is a broad discussion regarding Pesach—what about the rest of the year? https://www.amazon.com/Beef-Tallow-Goat-Shampoo-Conditioner/dp/B0CXYWXNZX?th=1

Answer:
Shampoo and other body lotions do not require kosher certification and may generally contain non‑kosher ingredients. However, when it comes to Biblical Basar Bechalav, it is forbidden to benefit from it. Accordingly, if a shampoo contains meat from a kosher animal together with milk from a kosher animal, it may not be purchased. The type of shampoo shown in the picture would therefore be prohibited. If, however, it can be verified that all ingredients were added cold and that no cooking or heat‑processing took place between the meat and milk components, then this would be a different discussion. In practice, however, shampoos are commonly produced using heat‑based industrial processes to emulsify and stabilize ingredients. As a result, it is generally assumed that ingredients are processed together under heat unless verified otherwise.

Sources

See regarding the Issur of Hanah by Basar Bechalav: Michaber 87:1; Tur 87:1; Rambam Sefer Hamitzvos Mitzvah 187; Machalos Assuros 9:1; Rebbe Yishmael in Chulin 115b

See regarding that it applies to all Kosher species: Beis Hillel 87:2; Kanfei Yonah 87; P”M 87 S.D. 16; Shaar Efraim 38; Machazik Bracha 87:15-17; Gilyon Maharsha ibid; Zivcheiy Tzedek 87:13 and 41; Aruch Hashulchan 87:12; Kaf Hachaim 87:19 and 56; Other opinions: Some Poskim rule that there is no prohibition to benefit from a mixture of Basar Bechalav is the meat is Neveila or Treifa. [Rambam in Pirush Hamishnayos Kerisus 3 [see Rambam La’am Machalos Assuros 9:6 footnote 29]; Degul Merivava 87:3 allows to be lenient like Rambam in a case of loss; Chasam Sofer ibid concludes that one who is lenient like the Noda Beyehuda has upon whom to rely; See Pischeiy Teshuvah 87:6; Yad Avraham 87:3]